Hecogenin azine and alkyliden-azinotigogenins



3,033,857 HECOGENIN AZINE AND ALKYLEN- AZINOTIGGGENINS The presentinvention relates to a method of separating hecogenin from a complexmixture of sapogenins and typically from mixtures of hecogenin withnon-oxo-sapogenins such as tigogenin, sarsasapogenin, diosgenin and thelike.

Such complex mixtures of sapogenins which contain hecogenin have in thepast been resolved by the application of various solvents to effect aselective solution of the desired compounds and fractionalrecrystallization from the crude mixtures. These prior processesarequite laborious and require numerous extractions andrecrystallizations to effect separation of products. The processes werenot eflicient and the compounds produced were of a low order of purity,

The present invention provides for an economical separation ofsecogenin, a valuable chemical for the preparation of such corticalsteroids as cortisone, by a simple process which can be carried outunder fairly primitive conditions.

According to the process of this invention the mixture of hecogenin withother sapogenins lacking an oxo-group (typically tigogenin) is treatedwith a hydrazine derivative of the type RNH-NH wherein R is hydrogen, alower alkyl radical or a CSNH radical. There is thus formed a hydrazonederivative of hecogenin as an oily liquid which is more soluble than thenon-oxo-sapogenin in polar solvents, and especially in lower alkanols.The oily hydrazone intermediates of the structural Formula 1:

can be conveniently converted to an azine of the structural Formula II:

3,933,85 Patented May 8, 1862 crystalline form and can be purified bywashing with solvents. The hydrolysis of the azines to hecogenin of avery high degree of purity can also be readily accomplished.

Hecogenin azines (the compound of the preceding Formula ll wherein R isa tigogenin-lZ-yl radical) can be conveniently prepared by one of thefollowing processes:

(a) The hydrazone is refluxed for about 3 minutes to an hour, typically10 to 30 minutes in an acid to which a small amount of ethanol or asolution of hydrogen chloride in ethanol can be added. The mixture isthen dried by evaporation of the acid to obtain the corresponding azine.Typically, the alcoholic filtrate containing the hydrazone derivative ofhecogenin after removal of the non-oxo-sapogenin is adjusted to pH 6 bythe addition of such acids as formic acid, acetic acid, or hydrochloricacid, after which the mixture is heated at reflux.

(b) The hydrazone solution, typically obtained after filtration from thetigogenin or other non-oXo-sapogenin, is vacuum distilled and thenheated for a period of three minutes to an hour at a temperature ofabout l220 C.

(c) The dry oily hydrazone of tigogenin is refluxed in a lower alkanolwith a small amount of pyridine hydrochloride for a period of about 10minutes to one hour, preferably 20 to 45 minutes. Thereafter, thesolution is rendered alkaline and heated until crystallization occurs.The solid is collected by filtration,

(d) The hydrazone of tigogenin is refluxed in high boiling solvents suchas tetralin or the monoethyl ether of ethylene glycol for a period of 10minutes to one hour.

Lower alkanol solvents useful in the foregoing procedure areparticularly ethanol, methanol, the propanols, tertiary butanol and thelike.

The foregoing procedures are particularly useful for the preparation ofhecogenin azine. However, it has also been found useful to carry out thecondensation of a hecogenin hydrazone of the Formula I with ketones andaldehydes. The lower alkanones, such as acetone, butanone, 2-pentanone,B-pentanone, 2-hexanone, and the like can be used. The resulting azinesof the formula 0 (lower alkyDz CH O tion. It is particularly convenientand economical to react the unsubstituted oily hydrazone of hecogeninwith a lower alkanone such as acetone to form the solid azine.

Pure hecogenin can be recovered from the azines of this invention byhydrolysis with acid, or by refluxing a solution of the azine in a loweralkanol alone or admixed with a less polar solvent such as chloroformfor 15 minutes to one hour at a pH of about 1 to 2.

The sapogenin mixtures in the examples given below were obtained byextraction of dry acid hydrolyzates of Mexican Agave fourcroyoides.Extracts of other plant species containing mixtures of hecogenin withnon-oxosapogenins can likewise be used for the isolation of hecogenin ofa high degree of purity of this procedure.

The azine compounds of this invention, their preparation and theirhydrolysis to pure hecogenin will be illustrated further in theexamples. These are given for the purpose of illustration only and arenot to be construed EXAMPLE 3 as limiting the invention in spirit or inscope.

The present invention is a continuation-in-part of copending applicationSerial No. 641,852 filed February 25,

10 grams of oily resinous hecogenin hydrazone, described in Example 2,are refluxed with 10 ml. of acetone for 60 minutes. The mixture iscooled to -5 C. and

1957 now Patent 3 5 the crystals are collected on the filter.12-isopropyliden- EXAMPLE 1 V azinotigogenin thus obtained can berecrystallized from a mixture of chloroform and acetone and then meltsat TWO grams of a K of a s m vcomammg about 206-208 C. The compound hasthe structural hecogenm and other genius lacking the l2-oxo group such fl as tigogenin, are dissolved in 20 ml. of ethanol and 4 ml. OwHm ofhydrazine hydrate are added. The reaction mixture is I refluxed for 24hours. The length of tirne required for N completion can be checked bydisappearance of the cari bonyl band from the infrared absorptionspectrum of the sample. After completion of the reaction, 12 ml. of 15solvent are distilled ed at atmospheric pressure. The residue is thenchilled, preferably at 0 C. for two hours, and the crystalline materialthus produced is filtered and 'i Washed with a small amount of ice coldethanol. Tigogenin thus obtained melts at about 194-198 c, l Thealkaline alcoholic filtrate containing hecogenin E0 hydrazone isadjusted to pH 6 with hydrochloric acid and refluxed for 15 minutes. Thehecogenin azine thus 01 Following the procedure of this example, butsubstituttained is filtered and washed with water. The compound ingmethylethyl ketone, diethyl ketone, m hy pr py ha th t u t al formulaketone, methylisobutyl ketone, or methylhexyl ketone for 0H: CH3 I HO VH0 As a modification of thisprocedure the alkaline ale acetone there areobtained respectively l 2- (2-butylholic filtrate containing hecogeninhydrazone is dried idine)azin tig g nin, 12-( -pcntyh 1a )azm0t1gcg mn,under vacuum and recrystallized repeatedly from amixl2-(4-methyl-2-pentylidmc) azinotigogemn and 12-(2-octure of ethylacetate and hexane to yield crystals melting tylidine)azinOtig0gcinatabout 205-207 C. Conversion to the azine can be 1 EXAMPLE 4 carriedout as above.

As a further modification thiosemicarbazide or a lower A 80111131011 05Z gIamS 0f sfiipogehlh mixture 111 alkylhydrazine hydrate, typicallyethylhydrazine hydrate, Of ethanol and 4 1111- Of y f hy are refluxedcan be substituted for the hydrazine hydrate. for 24 hours. The excesshydrazine is recovered for reuse by concentration of the, reactionmixture to dryness. EXAMPLE 2 The mixed dry residue obtained in theinitial reaction for 5 grams of the sapogenin mixture is refluxed for 12the preparation of the hydrazone derivative of hecogenin hours with amixture of 25 ml. of ethylene glycol monois refluxed in 10 ml. ofethanol and filtered from the inethyl ether and 5 ml. of hydrazinehydrate. 0.05 gram soluble residue of oxosapogenin. The non-oxosapogeninof activated carbon and 0.5 gram of diatomaceous earth in the solidfilter cake is dissolved in 10 ml. of ethanol are then added and themixture is filtered. The solution and concentrated to a volume of 7 ml.,chilled to 0 C. is chilled to 0 C. and the tigogenin crystals arefiltered, and allowed to stand for 24 hours to yield tigogenin. TheWashed with a small quantity of cold ethylene glycol solution of thehecogenin hydrazone is then adjusted to a monoethyl ether and dried. pHof 6 and heated under reflux for 15 minutes, concen-v The filtrate isdistilled to dryness under vacuum giving trated to a volume of 6 ml.,and chilled to 0 C. Crystals rise to an oily residue. Chromatography ofthis material of the hecogenln azine thus obtained are filtered, washedover an adsorbent composed of 85% silicon dioxide and 0 and dried.

15% of magnesium dioxide yields a colorless soil, which, EXAMPLE 5 whendried, is resinous material- 2 grams of hecogenin azine are refluxed for30 minutes Prolonged heating at 210 C. transforms the resinous i h 10 1,f $113 01, 10 m1, of chloroform, 2 ml. of

hecogenhl hydfazohe t0 the hecogehin alihe- Altemawater and 2 ml. ofconcentrated hydrochloric acid. Then y, the azihe can he formed'hyadlllstmfint 0f the 0.8 gram of sodium hydroxide in 2 ml. of water areadded,

ous material to pH 6 with mineral acid and refluxing for d th sob antsdi ill d ff il abundant m.

15 minuteszation has occurred. The suspension is then filtered andAccording to still another proced re, 3 grams of the the crystals arewashed with hot water and dried to obtain resinous hecogenin hydrazoneare refluxed for 30 minutes a good grade of hecogenin.

with 10 ml. of ethanol and 0.3 gram of pyridine hydro- EXAMPLE 6chloride. A crystalline solid precipitates out of this solution which isfiltered from the hot mixture and Washed Following the procedure of thepreceding example the with hot ethyl acetate to eliminate traces oftrigogenin alkylidineazinohecognenins described in Example 3 can andother sapogenins. Hecogenin azine thus obtained likewise be hydrolyzedto hecogenin. Sufficrent concenmelts at about 32933l C. tratedhydrochloric acid is used to lower the pH to l.

5 What is claimed is: 1. A compound of the structural formula wherein Ris a member of the group consisting of the tigogenin-lZ-yl radical andradicals of the formula (lower alkyl) (lower alkyl) 2. Hecogenin azine.3. A compound of the structural formula (lower alkyl) (lower alkyl) HO I4. l2-isopropylidenazinotigogenin. 5. The process for preparinghecogenin azine which comprises heating a member of the class consistingof the 40 wherein R and R' are lower alkyl radicals which comprisesheating of hecogenin hydrazone with a compound of the formula R-CO-R',wherein R and R are defined as hereinabove.

References Cited in the file of this patent UNITED STATES PATENTS WagnerOct. 8, 1946 Wagner Oct. 8, 1946 OTHER REFERENCES Fieser: NaturalProducts Related to Phenanthrene, 3rd Ed., (1949), pages 308-309.

Miramontes et '21.: Chem. & Industry, Nov. 29, 1958, page 1595.

1. A COMPOUND OF THE STRUCTURAL FORMULA
 8. THE PROCESS FOR PREPARING ACOMPOUND OF THE STRUCTURAL FORMULA